Sails for vessels are known, in particular but not exclusively cruise sails and regatta sails, which use the kinetic energy of the wind or canalizations thereof to confer a propulsive thrust to said vessels.
Sails are normally bent to a mast and cooperate with a boom at the base, or are bent or cooperate with a mainstay. They are normally obtained by putting together sailcloths according to various theories or practical embodiments.
Sails that are known and seen in nautical activities, unless they are small size sails for windsurfing, all have at least an overlap line, in which two parts or sailcloths of a sail are stably joined together.
The overlap line, especially where the nautical activity has to exploit to the utmost the thrusting action of the wind, entails poorer performance, although limited.
It is therefore a disadvantage of this type of known sail, as used in cruise and regatta vessels, that the overlap lines contradict the content of the patents that should protect said sails, but in practice give valid results only on paper.
Furthermore, one problem of known sails as used in cruise and regatta vessels that arises in nautical activity is the continuity of the surface. This is a performance factor, and even small discontinuities, creating small vortexes, create an overall drop in performance of the sail. Such discontinuities can be created, for example, by the conformation of the material used, or by air bubbles trapped in the resin or glue that makes up the surface on which the wind flows. In order to eliminate the loss in performance that these discontinuities entail, it is therefore necessary, for example in a regatta, to try, obsessively and painstakingly, to recover each and every feature that can give even a minimally better performance.
Another disadvantage of known sails as used in cruise and regatta vessels is the construction of the sail in terms of strength and cost, especially where complex machines have to be used to make the sail and where, apart from the complex machines, the sail then has to be completed manually (for example by overlapping segments of sail).
Apart from the uncertainties of the auxiliary human intervention, the costs of such a sail increase, reducing the possibility of access to such high performance sails.
There is also the factor of strength (and conformation) of the sails: it is well known that sails are studied and made according to precise ranges of specific winds.
Document EP-A-1.114.771 describes a composite material for making a sail, comprising a pair of thin polymer films, suitable to obtain a sandwich inside which a layer is inserted, consisting of a two- or three-dimensional mesh. The known composite material also provides two layers of individual fibers, not parallel and mutually intersecting, disposed on each face of the mesh, each in direct contact with a respective flexible polymer film. The layers are bound to the mesh and the respective flexible films by means of a glue, and by carrying out a calendering operation.
Document U.S. Pat. No. 6,302,045 (US'045) describes a molded three-layer sail, obtained by rolling together three reinforced triangular layers of film in a mold. Each triangular layer is designed for a respective corner of the sail, that is, tack corner, head corner and clew corner. Each layer consists of a plurality of triangular parts that start from a respective one of the three corners of the sail, so that the parts in each layer overlap in the body of the sail. Each triangular layer includes a plurality of primary reinforcement elements in the form of threads, attached to one side of a film by means of a layer of adhesive applied to the film. These reinforcement elements in the form of threads run parallel to and distanced from each other, parallel to a long side, from the peak of the triangle. Possibly, additional transverse reinforcement threads or elements may also be present. With the construction proposed in US'045, the parallel reinforcement threads of each triangular layer are transverse and intersect with the threads of the other triangular layers, because the threads run from a respective peak of the triangular layer, which for the three triangular layers will be respectively the tack corner, the head corner and the clew corner, which cannot overlap.
The present invention therefore has a plurality of aims and purposes, all suitable to overcome the limits of the state of the art as identified above, and also to give other advantages as will be evident in the following description.
It is therefore one purpose of the present invention to obtain a truly integral sail, that is, without external overlapping of two or more important parts of the sail.
It is also a purpose of the present invention to obtain a sail having a smooth surface on both sides and hence without discontinuities, even small ones, created by possible air bubbles or other in the material (resin or glue) that makes up the surface on which the wind flows.
It is also a purpose of the invention to obtain sails suitable to be used in a range of winds, also comprising very fast winds.
Another purpose of the present invention is to perfect a method that allows to obtain sails with operative continuity, simply and fast.
It is also a purpose to obtain sails having a profile suitable both for the type of sailing for which they are designed, and also for the type of wind for which they are made.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.